Lazy initialization for ProcessesEventRouter.

chrome/browser/extensions/event_router.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_EVENT_ROUTER_H_
 #define CHROME_BROWSER_EXTENSIONS_EVENT_ROUTER_H_
 
 #include <map>
 #include <set>
 #include <string>
 #include <utility>
 
 #include "base/compiler_specific.h"
 #include "base/memory/linked_ptr.h"
 #include "base/memory/ref_counted.h"
 #include "base/values.h"
 #include "chrome/browser/extensions/event_listener_map.h"
 #include "chrome/common/extensions/event_filtering_info.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "ipc/ipc_sender.h"
 
 class GURL;
-class ExtensionDevToolsManager;
 class Profile;
 
 namespace content {
 class RenderProcessHost;
 }
 
 namespace extensions {
 class Extension;
 class ExtensionHost;
 class ExtensionPrefs;
 
 struct Event;
 
 class EventRouter : public content::NotificationObserver,
                     public EventListenerMap::Delegate {
  public:
   // These constants convey the state of our knowledge of whether we're in
   // a user-caused gesture as part of DispatchEvent.
   enum UserGestureState {
     USER_GESTURE_UNKNOWN = 0,
     USER_GESTURE_ENABLED = 1,
     USER_GESTURE_NOT_ENABLED = 2,
   };
 
+  // Observers register interest in events with a particular name and are
+  // notified when a listener is added or removed for that |event_name|.
+  class Observer {
+   public:
+    // Called when a listener is added.
+    virtual void OnListenerAdded(const std::string& event_name) {}
+    // Called when a listener is removed.
+    virtual void OnListenerRemoved(const std::string& event_name) {}
+  };
+
   // Sends an event via ipc_sender to the given extension. Can be called on any
   // thread.
   static void DispatchEvent(IPC::Sender* ipc_sender,
                             const std::string& extension_id,
                             const std::string& event_name,
                             scoped_ptr<base::ListValue> event_args,
                             const GURL& event_url,
                             UserGestureState user_gesture,
                             const EventFilteringInfo& info);
 
   EventRouter(Profile* profile, ExtensionPrefs* extension_prefs);
   virtual ~EventRouter();
 
   // Add or remove the process/extension pair as a listener for |event_name|.
   // Note that multiple extensions can share a process due to process
   // collapsing. Also, a single extension can have 2 processes if it is a split
   // mode extension.
   void AddEventListener(const std::string& event_name,
                         content::RenderProcessHost* process,
                         const std::string& extension_id);
   void RemoveEventListener(const std::string& event_name,
                            content::RenderProcessHost* process,
                            const std::string& extension_id);
 
   EventListenerMap& listeners() { return listeners_; }
 
+  // Registers an observer to be notified when an event listener for
+  // |event_name| is added or removed. There can currently be only one observer
+  // for each distinct |event_name|.
+  void RegisterObserver(Observer* observer,
+                        const std::string& event_name);
+
+  // Unregisters an observer from all events.
+  void UnregisterObserver(Observer* observer);
+
   // Add or remove the extension as having a lazy background page that listens
   // to the event. The difference from the above methods is that these will be
   // remembered even after the process goes away. We use this list to decide
   // which extension pages to load when dispatching an event.
   void AddLazyEventListener(const std::string& event_name,
                             const std::string& extension_id);
   void RemoveLazyEventListener(const std::string& event_name,
                                const std::string& extension_id);
 
   // If |add_lazy_listener| is true also add the lazy version of this listener.
@@ skipping 156 matching lines @@
                             ExtensionHost* host);
 
   // Implementation of EventListenerMap::Delegate.
   virtual void OnListenerAdded(const EventListener* listener) OVERRIDE;
   virtual void OnListenerRemoved(const EventListener* listener) OVERRIDE;
 
   Profile* profile_;
 
   content::NotificationRegistrar registrar_;
 
-  scoped_refptr<ExtensionDevToolsManager> extension_devtools_manager_;
+  EventListenerMap listeners_;
 
-  EventListenerMap listeners_;
+  typedef std::map<std::string, Observer*> ObserverMap;
+  ObserverMap observers_;
 
   // True if we should dispatch the event signalling that Chrome was updated
   // upon loading an extension.
   bool dispatch_chrome_updated_event_;
 
   DISALLOW_COPY_AND_ASSIGN(EventRouter);
 };
 
 struct Event {
   std::string event_name;
@@ skipping 18 matching lines @@
         Profile* restrict_to_profile,
         EventRouter::UserGestureState user_gesture,
         const EventFilteringInfo& info);
 
   ~Event();
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EVENT_ROUTER_H_